Non-Test Cubes for Test Generation Targeting Hard-to-Detect Faults

A test set includes a significant amount of information about input assignments that prevent the faults that it does not detect from being detected. The procedure described in this paper extracts this information and uses it to guide an efficient test generation process that is fundamentally different from existing processes. Even with limited computational complexity, this new process is able to generate tests for hard-to-detect transition faults that are not detected by a test set that consists of both broadside and skewed-load tests. The basic idea is the following. Let t be a test that does not detect a fault f. The procedure extracts from t a minimal subset of values that prevent f from being detected. These values are included in a partially-specified test, which is referred to as a nontest cube. In a basic step, the procedure finds a nontest cube for f based on t. It then modifies t by complementing one specified value of the nontest cube to ensure that it does not prevent f from being detected. This is repeated until a test is found or a termination condition is reached. The nontest cubes are also used for finding necessary assignments and identifying undetectable faults.